The overall objectives are to find out how matrices of collagen fibers are made. Type V collagen is a member of this family of proteins and while it occurs widely associated with cells, it is particularly found in muscles. We have discovered soluble precursors, procollagens, to type V collagen in several chick embryo tissues. In particular we are studying the biosynthesis and sequential processing of this material in blood vessels, where it may play an important part in development, growth, and the progression of pathological lesions. We plan to define further the biosynthetic sequence of this and other collagens in normal tissues.